Testing and troubleshooting networks

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Testing and troubleshooting networks

  1. 1. Testing and Troubleshooting Networks
  2. 2. Network troubleshooting Tools• The various tools available for checking the network are: – Software Tools – Hardware Tools – Touchy Tools
  3. 3. Loopback Test• Signal is transmitted and it echos back• Echo signal compared with original signal• Tests the transmission path and tools used for transmission• Traces a faulty node in network• Requires a loopback plugChapter 4 3
  4. 4. Network Monitors• Detect and display problems present in the network• Provides data related to network traffic• Analyze data traffic to determine various network problems that can occur
  5. 5. LAN Tester - I• Used to test 10, 100 and 1000 Base- T Networks• Consists of two units – Main unit • Indicates LAN device type i.e hub, switch • Determines speed of LAN and type of link – Remote Probe • Used to locate faults in a cableChapter 4 5
  6. 6. LAN Tester - II• Functions of LAN tester – Verify PC to hub speed and data transmission – Check hub to hub data transmission – Determines any speed bottlenecks present on 10 and 100 Base-T LANs – Continuously tracks LAN link
  7. 7. Cable Testers and Certifiers• Checks electrical connections• Determines if a short or open circuit is present in the network• Consists of a source of current, volt meter and microcontroller
  8. 8. Time-Domain Reflectometers• Locates fault in metallic cables• Transmits a pulse through the cable• At every discontinuity, an echo is reflected back• Used to test long cables• Results are displayed on a CRT or LCD
  9. 9. Protocol Analyzers - I• It may be a software or hardware device• Captures packets from network• Analyzes captured packets• Analyzes the network traffic• Identifies bottlenecks in network• Operate on network layer• Identifies active systems on network• Removes the faulty system from network
  10. 10. Protocol Analyzers - IITypes of protocol analyzers – Packet analyzer • Capture packets present on the wire and store them for analyzing later • Does a statistical analysis of the data captured but it is not its primary function – Statistical analyzers • Gather quantitative data to prepare a report on the different statistical trends • Does not store the packets for later analysis
  11. 11. Touchy Tools• Used to identify network problems• Problems are identified using asking various questions to user• Analyzes current situation and compares it with set of baselines• Adequate knowledge and experience is useful to determine problems
  12. 12. Backups• Used to preserves a copy of original files• Should be performed on regular basis• Useful when a data loss occurs• Restores system to previous state
  13. 13. Baselines• Used to compare the system’s current performance with reference level set by the network administrator• Determines possible network problems• Performance monitor helps to set baselines• Monitors both real time as well as historical data• Baselines may change with time
  14. 14. Troubleshooting Model - I• Steps of troubleshooting model – Establish the symptoms – Isolate the cause of the problem – Establish what has changed that might have caused the problem – Ask Isolating questions
  15. 15. Troubleshooting Model - II– Identify the most probable cause– Implement a solution– Test the solution– Recognize the potential effects of the solution– Document the solution
  16. 16. Four layer Model• Four layers model – Hardware – Considers all the hardware related issues • Focuses on problems with network devices such as hubs, switches – Protocols – Deals with problems related to protocols • Checks the installation and configuration of protocols – Network – Considers the client and server concept • Determines which node will act as client and which will act as server – Shared Resources – Determines which resources are to be shared
  17. 17. Cable Testing and Certification - I• Cable Distance – Measures the distance of a cable and helps to locate the point where a short or open is present – Speed of pulse depends on wires, type of insulation and external shielding• Wire Map – Used for twisted-pair installations – Detects split pairs – Detects crossed pair condition
  18. 18. Cable Testing and Certification - II• Attenuation – Reduction in strength of signal – Cable Testers are used to measures loss of power• Near-End Crosstalk – Transfer of electricity from one wire to another in the same cable – Causes • Untwisted patch cables • Crossed pairs
  19. 19. Cable Testing and Certification - III• Network Monitoring and Protocol Decoding – Cable checkers monitor network traffic • Detects high or low level traffic – Locates loose cables• Noise-Level Test – External signal that interfere with original signals – Measured in millivolts (mV)• Testing Fiber – Fiber-optic cable testers use optical time-domain reflectometer which depend on the reflection of light
  20. 20. SNMP• Simple Network Management Protocol• Networking standard protocol• Used with TCP/IP networks• Monitors and manages the network• Helps to examine network performance• Detect network faults or inappropriate access
  21. 21. Potential Network connectivity problem• Causes of network connectivity problems – Incorrect network adapters (NIC) – Incorrect switch settings – Faulty hardware – Driver issues – Upgradation of operating system – Server relocation – The network adapter is incompatible with the motherboard
  22. 22. Network Workstation Troubleshooting Process• Steps to troubleshoot network workstation – Determine what stopped working – Determine if failure is on a single user’s workstation – Try to log onto the network – Check the NIC’s link light
  23. 23. Netstat Command• Displays TCP/IP information• Determines which ports are active• Identifies ports that are vulnerable to attacks• Provides connection details• Provides data about TCP and UDP
  24. 24. Ipconfig Command• Displays all network settings• Identifies DHCP problems• Used with windows 2000 and later versions• Displays and resets DNS cache• Sets and displays DHCP class IDs for an adapter
  25. 25. Winipcfg Command• Provides IP addressing details• Used for windows 98 or earlier versions• Provides details such as IP address, Subnet Mask, Default Gateway, DHCP Server, WINS Server, etc.
  26. 26. ARP Command• Links IP address of a node with its hardware address• Various ARP command options can be used to display or change the values in ARP table
  27. 27. Nbtstat Command• Resolves NetBIOS name resolution problems• Used when WINS server is not accessible• displays protocol information and current TCP/IP connection using NetBIOS over TCP/IP (NBT)
  28. 28. Route Command• Allows you to view and make changes in the IP routing table• Used to differentiate between routes to hosts and routes to networks by reading the network address of the destination

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